During formation of a FinFET structure, a source/drain portion including a cap layer and an epitaxial layer may be hurt by several etching processes. If the source/drain portion is hurt, after a gate metal layer is formed within the FinFET structure, a silicon fin of the FinFET structure may be in direct contact with an epitaxial silicon definition layer of the Fin structure. Therefore, leakage of the gate metal layer may be introduced, and operation failure may occur because of the leakage.